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Fluorescence and Food Safety 江南大学理学院 陈国庆 cgq2098@jiangnan

Fluorescence and Food Safety 江南大学理学院 陈国庆 cgq2098@jiangnan.edu.cn. 农药污染. 苏丹红事件. 三聚氰胺事件. 食品安全不容忽视 !. 2005-2008 年的食品安全事件. 2005 年. 1 、苏丹红事件席卷全国 2 、立顿速溶茶涉嫌氟超标 3 、雀巢奶粉被指碘超 4 、光明被指回收过期变质奶再生产 5 、啤酒甲醛风波引发消费者恐慌 6 、哈根达斯深圳黑作坊被查 7 、鲮鱼罐头在港被检出孔雀石绿. 2006 年. 1 、福寿螺致病 2 、人造蜂蜜事件 3 、毒猪油事件

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Fluorescence and Food Safety 江南大学理学院 陈国庆 cgq2098@jiangnan

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  1. Fluorescence and Food Safety 江南大学理学院陈国庆 cgq2098@jiangnan.edu.cn

  2. 农药污染

  3. 苏丹红事件

  4. 三聚氰胺事件 • 食品安全不容忽视!

  5. 2005-2008年的食品安全事件 2005年 1、苏丹红事件席卷全国 2、立顿速溶茶涉嫌氟超标 3、雀巢奶粉被指碘超 4、光明被指回收过期变质奶再生产 5、啤酒甲醛风波引发消费者恐慌 6、哈根达斯深圳黑作坊被查 7、鲮鱼罐头在港被检出孔雀石绿

  6. 2006年 1、福寿螺致病 2、人造蜂蜜事件 3、毒猪油事件 4、“口水油”沸腾鱼 5、瘦肉精中毒 　 6、大闸蟹致癌 7、“苏丹红”鸭蛋 8、“嗑药”的多宝鱼 9、有毒的桂花鱼 　 10、陈化粮事件 　

  7. 2007年 1、龙凤与思念问题速冻食品深圳撤柜07/04/12 2、上海星巴克售过期苹果汁07/07/30 3、五粮液幸运星糖精超标07/11/01 4、北京王致和豆腐乳被指保质期内发霉07/11/08 5、味全食品旗下奶粉被查出致病菌07/11/21 6、台湾婴儿配方奶粉检出致病菌07/11/27 7、香港的Godiva朱古力遭停售07/12/03 8、乐事薯片等23种进口食品抽查不合格07/12/10 9、南昌：统一方便面吃出烟头07/12/12 10、浙江义乌：多美滋奶粉中出现小蛆 08/01/0

  8. 三聚氰胺…… 2008年

  9. “苏丹红”辣酱、毛发酱油、石蜡火锅底料、瘦肉精、毒大米、地沟油劣质奶粉养出大头婴儿、粉丝掺假添加有毒化学肥料、广州假酒中毒致多人死亡…… 救命啊！食品安全、人命关天

  10. 目 录 一、分子荧光光谱 二、荧光光谱技术在食品安全中的应用

  11. 一、分子荧光光谱 1、What is Fluorescence? （Historical Overview - Fluorescence） Fluorescence is an emission of light (luminescence) that is usually found as an optical phenomenon in cold bodies. The absorption of a photon causes the emission of another photon with a longer wavelength. The energy difference between the absorbed and emitted photons ends up as molecular vibrations or heat.

  12. First Reference Mention of fluorescence and phosphorescence phenomenon found in Chinese texts dating back to 1500BC. Associated with medicine for many centuries. 1565: Report of a medicine treating kidney stones: Water containing wood from the Narra tree. This solution glows when exposed to sunlight Wood and knowledge imported from middle America to Europe. Nicolas Monardes

  13. John Frederick William Herschel (1792-1871) First Reference in Scientific Paper 1845: Report of Quinine emission when excited by sunlight

  14. George Gabriel Stokes (1819-1903) Discovery of the Stokes Shift 1852: Observation that emitted wavelengths are longer than exciting wavelengths. Fluorescence was the name given as a description of the part of the mineral fluorite, composed of calcium fluoride, which produced a visible emission when illuminated with UV radiation.

  15. Sn Tn S3 T3 S2 T2 S1 intersystem crossing T1 Alexander Jablonski (1898-1980) ground state absorption fluorescence phosphorescence S0 The Jablonski Diagram The Jablonski diagram illustrates absorption, emission as well as vibrational (heat) and intersystem effects.

  16. Potential Excited State (S1) Ground State (S0) Generalised Coordinates The Franck-Condon Principle 1925: Proposal for electronic transitions. 1926: Quantum mechanical formulation. J. Franck (1882-1964) E.U. Condon (1902-1974)

  17. DNA conformation peptide cleavage Förster’s Theory 1947: Theory of radiationless energy transfer Original work: randomly distributed molecules The real value: distance measurements of rigid pairs Theodor Förster (1910-1974) protein hydrolysis conformational changes ligand-receptor interaction fusion of lipid vehicles

  18. 2、产生荧光的条件 (1)物质的分子必须具有吸收结构 (2)物质分子必须有一定的荧光量子产率 (3)适宜的环境

  19. 3、荧光特性 The luminescence emitted by a sample can be characterised by five parameters. • excitation wavelength • emission wavelength • emission intensity • quantum yield • polarisation • decay time

  20. 4、分子荧光光谱的分类 （1）常规荧光光谱 （2）同步荧光光谱 （3）时间分辨和相分辨荧光光谱 （4）偏振荧光光谱 （5）低温荧光光谱 （6）空间分辨荧光光谱 （7）导数荧光光谱 （8）其它

  21. 5、荧光光谱的应用 荧光光谱分析具有灵敏度高、准确度高、选择性高和取样少、方便、快捷、适用范围广的优点，它作为一种常用的光谱分析技术已经被广泛应用到各个领域。

  22. Application Fields Analytical ChemistryPharmacology • Measurement of extremely low analyte • Monitoring of drug interaction with concentrations biological systems • Identification and detection of single molecules • Anaesthesiology research • Analysis of complex mixtures of fluorescent • Quality control substances • High throughput screening Biochemistry and MedicinePhotophysics and PhotoChemistry • Drug monitoring in photodynamic therapy • Characterisation of excited states • Investigation of protein structure and folding dynamics of molecules • Investigation of protein-antibody interactions • Electron and proton transfer • Determination of donor-accepter distances • Intra-molecular relaxations • Investigation of permeability and structure of • Michelle structure and reaction kinetics membranes in molecules • Enzyme research in proteins and membranes • Excimer and exciplex formation • Investigation of dynamics and structure of • Polymer structure and dynamics nucleic acids • Solvent-solute interactions • DNA-sequencing and sizing • Study of monolayers and surfaces • Photosynthesis research

  23. Chemical Applications There are several ways in which fluorescence is needed in scientific research: Most basic need: understanding the sample - emission and absorption What does this tell us? How can we use this: Discover effects of local environment, energy transfer, can be used as a label for interactions.

  24. Fluorescence Detection of Explosives To distinguish fluorescence of Explosives from Standard Fluorescence of materials a comparison has to be made

  25. Fluorescence Detection of Explosives Semtex Fluoresces in similar range as clothing. Therefore difficult to detect optically

  26. Tryptophan Measurements Tryptophan is a standard Amino Acid and is an essential amino acid for many organisms. Therefore is interaction mechanisms are probed. It is also a useful protein to study conformational changes.

  27. DNA Fluorescence Measurements Many Biological reactions can be monitored by studying the change in spectroscopic data with the addition of reagents to a system. For the case of DNA, fluorescence can be used to identify when certain Enzymes react with the DNA as the spectra changed when the enzyme binds to the DNA.

  28. Fluorescence Lifetime Excimer formation - takes place at only at relatively high concentration dept. on monomer conc. Monomer has two decay times Excimer has a rise and a decay timeshort decay time of monomer = rise time of excimer; decay time of excimer = long decay time of monomer Excimer Emission lex= 335nm lem= 465nm Monomer Emission lex= 335nm lem= 395nm Sample: pyrene in cyclohexane concentration 10-2M Fit result: double exponential global fit: tM=9.3ns, tE=15.4ns

  29. InGaAs / InP Quantum Well Measured Using 760nm Laser diode excitation and a NIR-PMT em= 920 nm (green curve) substrate: em= 1330 nm (red curve) quantum well Double exponential decay components of 1.7ns and 6.0ns

  30. TemperatureInformation on structure of sample and energy bands Emission spectrum of triphenydiamine as a function of temperature from 90-107K. Pyrene in cyclohexane measured at room temperature and at liquid nitrogen temperature.

  31. Phosphorescent Resonant Energy Transfer between Iridium Complexes, Wasserberg et al J. Phys. Chem. A, Vol. 111, p1381, 2007 Pyrene in cyclohexane measured at room temperature and at liquid nitrogen temperature.

  32. Anisotropy of Dendrimers ADSB Dendrimer with different generations, light harvesting system

  33. Anisotropy of Dendrimers Steady State Anisotropy

  34. Anisotropy of Dendrimers Anisotropy decay is constant and same as steady state – very fast depolarisation

  35. Anisotropy of Dendrimers Different Cored System

  36. Anisotropy of Dendrimers Decay of Anisotropy – slow depolarisation

  37. Flipped cytosine base Fluorescence as a Probe of DNA Dynamics Investigating DNA-Protein Interactions The building blocks of DNA and RNA are nucleotides. These naturally occurring nucleotides are non-fluorescent, so in order to study important macromolecules such as DNA using fluorescence spectroscopy, a fluorescence probe must be introduced into the system. X-ray crystal structure of DNA duplex bound by the Hha1 enzyme A commonly used probe is an analogue of the adenine base and is called 2 aminopurine (2AP). Adenine is one of the four component bases of both DNA and RNA, as such 2AP can be inserted into a DNA strand in place of an adenine base without significantly disturbing the conformation of the DNA.

  38. Bound DNA Free DNA Fluorescence as a Probe of DNA Dynamics Investigating DNA-Protein Interactions The fluorescence of 2AP has been used to study base flipping. Base flipping is the mechanism of interaction between the DNA helix and many enzymes and other proteins. After labelling a solution of DNA duplex with 2AP, the fluorescence lifetime is monitored as the enzyme Hha1 is added to the solution. Decay curves for 2-AP labelled free DNA and Hha1 bound DNA A marked difference in the fluorescence decay curves for the unbound DNA duplex compared to that of the protein bound duplex with the 2AP flipped into the Hha1 enzyme active site was observed. This behaviour is consistent with the proposed “base flipping” mechanism by which Hha1 is thought to act.

  39. FRET Fluorescence resonance energy transfer (FRET) is a process involving the radiationless transfer of energy from a "donor" fluorophore to an appropriately positioned "acceptor" fluorophore. • Donor molecule is excited • Donor relaxes by transferring • its energy to acceptor molecule • No photons involved in FRET process • Energy transfer is a result of long range • dipole-dipole interaction kT kF

  40. Fluorescence Resonance Energy Transfer FRET Analysis of peptide linker fused protein domains as FRET sensors. Merkx et al, Biochemistry 2006, 45, 13183

  41. Application :Phosphor properties for flat panel displays The excitation and emission spectra of :- CaS:Eu, Ca Sr S;Eu and SrS:Eu . The emission spectra were measured at an excitation wavelength of 470nm. . A shift in the emission spectrum to shorter wavelengths, corresponding to a higher luminance, was demonstrated. This has proved the viability of partial ion replacement as a method to increase the luminance of CaS and increase the viability of CaSrS:Eu as a red emitting electroluminescence phosphor material.

  42. - YAP - LSO(Ce) - PWO X-Ray Excitation Emission of Caesium Doped Compounds or Measurement conditions Integration time: 0.2s Excitation: X-ray Various X-Ray Spectra X-Ray

  43. Characterisation of Synchrotron Crystals or Scintillator Crystals • Widely used for PET (Positron Emission Tomography) • Gamma Ray detection (scintillation) • Gamma Rays are absorbed by certain materials which then emits beta-radiation (positron) • Fluorescence studies can optimise material understanding X-Ray

  44. 二、荧光光谱技术在食品安全中的应用 实验仪器 SP-2558多功能光谱测量系统 SP-2558 multifunctional spectrometer system

  45. 1、白酒的荧光光谱检测 1.1 醇类物质的荧光光谱分析 (1) 甲醇的荧光光谱

  46. 不同波长的紫外光照射100%甲醇(光谱纯)液体的荧光光谱图

  47. 波长为230 nm光激励不同浓度甲醇溶液的荧光光谱

  48. 光谱纯乙醇液体在不同紫外光激励下产生的荧光光谱 (2) 乙醇的荧光光谱

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